Bad Milo (2013)

Duncan is an average guy who works at an average office job. But he starts to get pains in his stomach whenever he feels stressed out. Things get worse every time he tries to just hide his stress, by burying it inside. It all comes to a head when that "stress" is turned in to an actual little beast that exits his body via his butt and takes revenge on the things that stress him out. But it soon starts to threaten the one thing he loves, his wife.